1. Field of the Invention
The present invention relates to a suction or blowing apparatus and/or pneumatic conveying apparatus for conveying various types of dust and bulk material, particularly difficultly pneumatically conveyable material such as leaves, cotton, chips or the like. The apparatus includes two tubes which are arranged one within the other, wherein the inner tube projects into a narrowing portion of the outer tube and the inner tube and the outer tube form an injection nozzle, wherein propellant air can be admitted to one of the tubes.
2. Description of the Related Art
An apparatus of this type is already known from German Utility Model 8 317 867.8. The apparatus is a vacuum cleaner for motor vehicles, wherein the inner tube is connected to the exhaust pipe of the automobile and the outer tube is connected to a suction hose. In accordance with the air jet-vacuum pump principle, the flow velocity of the exhaust gases is utilized in order to generate a negative pressure which acts on the suction hose to create the suction effect. However, this suction effect is not very great in this known apparatus, because the suction duct consisting of suction hose and outer tube has a rectangular deflection in the region of connection of the two components, so that a high resistance to the flow of the air to be sucked off occurs. The narrowing portion of the outer tube is another disadvantage because the narrowing portion can be clogged with the material being conveyed, particularly difficultly pneumatically conveyable material.